We will continue to study the regulation of glucose metabolism in skeletal muscle at rest and during exercise. In particular, we will attempt to assess the basis for the increase in insulin sensitivity which we have observed in skeletal muscle during the recovery period after exercise and the decrease in activity which we have observed with aging. These investigations will entail an assessment of insulin binding to incubated muscles. In adddition, we will attempt to determine whether differences in sensitivity involve alterations in the glucose transport system or in one or more of the intracellular events of glucose metabolism.